Non-polar Blackgates replace polarized?

[reiver]

I'm was looking at the analog pre-amp-out circuit board on my receiver (Denon AVR-3805) and noticed that the signal passes through two electrolytic capacitors before it reaches each RCA jack.

These caps are prime to upgrade obviously, but here's my question:


The stock caps are 22mf/50v polarized caps, as you can see on the attached schematic. Can I replace these with non-polarized 22mf Blackgate electrolytics, or is there reason the stock ones are polarized?

-Bryan

[SQLGuy]

Electrically, yes you can use them.

Bipolar electrolytics are actually two electrolytic capacitors connected in series in one case. So, instead of 1 22uF cap, you're putting in 2 44uF caps in series (which divides the effective capacitance but protects both caps from reveresed polarity).

I would say to bypass such a coupling cap with a good quality foil cap (.1 uF or so). i.e. Put in the bipolars, but also put a .1uF Wima or something in parallel with each of them.

[MRupp]

Bipolar electrolytics are actually two electrolytic capacitors connected in series in one case.

All electrolytic caps are actually 2 caps in series. Polar caps have only one foil that was formatted to build an oxide layer of the required thickness while the second foil has just the thin oxide layer that forms under atmospheric conditions - and survives 1 - 2 Volts. The non-polar cap has both foils formatted to sustain the nominal voltage.

[reiver]

NP caps block DC while polarized ones pass it.

What I was hinting at was whether this type of circuit actually requires polarized caps...and if switching to NP versions could cause some instability in the circuit.

[SQLGuy]

Originally posted by reiver
NP caps block DC while polarized ones pass it.

No, that's entirely wrong. The only type of cap that passes DC is a bad one.

Non-polarized caps can take DC offset in either direction. Polarized caps can take it in one direction only.

If you take your 22uF 50V NP's, you can apply, for example, +35V to one leg and ground to other, or vice versa, and in either case things will be just fine.

If you try the same thing with a polarized cap, things will only be fine with +35V on the + leg. If you reverse it, the cap will start to get hot, and will eventually vent or explode.

[reiver]

Thanks for the info, I didn't know NPs could pass DC, explains some things about modding that never seemed to click with me. Time to order some Blackgates....